p.111 of the regulations gives an example specifically of a UAS that uses the internet connection of a paired smartphone:
> Charlie’s UAS is designed to pair with his smartphone to transmit the remote identification message elements through an internet connection to a USS. Because Charlie’s UAS cannot broadcast [i.e. radio] remote identification message elements, it does not function unless his smartphone is connected to the internet and transmitting through that internet connection to Bravo USS.
That doesn't seem remotely practical. Even the tiniest hobby drones can easily and safely get 150ft away along the ground and are allowed to go up to 400ft.
Have you tried connecting to a phone's hotspot or bluetooth line of sight from 50ft away? 75ft? That's like half a second of flight time for drone then it's supposed to just "stop operating". Sounds incredibly dangerous and ineffective to me.
If its from the base station that would probably make more sense but that would require replacing controllers which are the most costly portion of amateur setups (besides FPV setups).
The proposed document contains answers to most of your questions. I'd recommend using search to jump around to the areas you seem interested in.
> For both standard and limited remote identification UAS, at this time the FAA has not proposed any requirements regarding how the UAS connects to the internet to transmit the message elements or whether that transmission is from the control station or the unmanned aircraft. The FAA understands, however, that there are concerns about the impact that connecting to the internet directly from the unmanned aircraft (as opposed to the control station) could have on networks that use radio frequency spectrum, including interference, network stability, or other
effects.
If you want to fly 400 ft away, it doesn't seem too onerous to require a communication setup that's capable of staying in contact with your drone.
> Charlie’s UAS is designed to pair with his smartphone to transmit the remote identification message elements through an internet connection to a USS. Because Charlie’s UAS cannot broadcast [i.e. radio] remote identification message elements, it does not function unless his smartphone is connected to the internet and transmitting through that internet connection to Bravo USS.